CN111884175A - High-voltage cable metal sheath grounding circulation restraining method based on electromagnetic coupling method - Google Patents
High-voltage cable metal sheath grounding circulation restraining method based on electromagnetic coupling method Download PDFInfo
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- CN111884175A CN111884175A CN202010771515.7A CN202010771515A CN111884175A CN 111884175 A CN111884175 A CN 111884175A CN 202010771515 A CN202010771515 A CN 202010771515A CN 111884175 A CN111884175 A CN 111884175A
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- 230000000452 restraining effect Effects 0.000 title claims abstract description 23
- 230000001629 suppression Effects 0.000 claims description 7
- 229910000976 Electrical steel Inorganic materials 0.000 claims description 5
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- 238000004804 winding Methods 0.000 claims description 5
- 239000004593 Epoxy Substances 0.000 claims description 3
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- 230000008878 coupling Effects 0.000 abstract description 13
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/22—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for distribution gear, e.g. bus-bar systems; for switching devices
- H02H7/228—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for distribution gear, e.g. bus-bar systems; for switching devices for covered wires or cables
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Abstract
The invention provides a method for restraining the circular current of a metal sheath of a single-core high-voltage cable based on electromagnetic coupling, which can connect a magnetic core at a cable terminal and restrain the grounding circular current of a cable at a primary side by serially connecting a resistor, an inductor and an impedance at a secondary side in an electromagnetic coupling mode.
Description
Technical Field
The invention relates to a high-voltage cable in a power supply and distribution network, in particular to a method for restraining grounding circulation of a metal sheath of a high-voltage cable based on electromagnetic coupling.
Background
Along with the development of the urbanization process, the single-core high-voltage cable is more and more widely applied to urban transmission and distribution networks. Because the alternating current passing through the cable core can cause an alternating magnetic field to be generated around the cable core, the metal sheath generates induced voltage due to the action of the changing magnetic field, and once the cable sheath is grounded, circulating current can be generated. To protect against excessive sheath induced voltage and sheath circulating current, high voltage cables are typically grounded using a metal sheath cross-connect grounding scheme to suppress induced voltage and thereby reduce circulating current. However, the induced voltage of the metal sheath is unbalanced due to different core currents, uneven cable segmentation, unequal cable spacing, different cable arrangement modes and other factors, so that the ground circulation is generated. The problem of large grounding current of the cable is increasingly highlighted due to the fact that a large number of single-core high-voltage cables are put into operation, and therefore research on generation and pre-control of grounding circulation currents is needed, and a method for reducing the grounding circulation currents is analyzed. Through research of domestic and foreign personnel, the method for connecting the resistor, the inductor, the compensation inductor and the like in series at the cable terminal can effectively inhibit the cable circulation. The series resistor and the inductor have good effect of inhibiting the circulating current, and the effect of inhibiting the circulating current by the compensation inductor is poor due to the fact that the current phase sequence of the cable core is fixed. Therefore, three methods of terminal series resistance, inductance and simultaneous series resistance and inductance are widely adopted by the cable in practical operation to inhibit the circulating current of the cable. However, in the case of a series resistance, an inductance and a simultaneous series resistance inductance at a cable termination, the increase in the total impedance of the cable sheath may cause a rise in the termination voltage, especially when there is a sudden increase in the cable circulating current, which may cause serious damage to the cable sheath as specified in GB 50217 "design specifications for electrical cables for power engineering": the maximum value of the normal induction potential at any point on the metal layer of the alternating current single-core power cable which is not directly grounded meets the following regulations: when safety measures capable of effectively preventing personnel from contacting the metal layer at will are not taken, the voltage is not more than 50V; except for the above, it should not be more than 300V. It has been found that when the cable circulating current suddenly increases, the voltage at the end of the sheath can easily exceed 50V, and the series resistance, inductance and at the same time the series resistance and inductance can break down due to the excessive voltage, so that a larger capacity device is usually selected for installation, which undoubtedly increases the cost greatly. Therefore, the method for restraining the circulation current must be optimized, the purpose of reducing the circulation current is achieved, and meanwhile, the voltage of the sheath is ensured to be within a safe range.
According to the invention, through researching the circulating current restraining method of the existing terminal simultaneously connected with the resistance inductor in series, the high-voltage cable metal sheath grounding circulating current restraining method based on the electromagnetic coupling method is adopted under the requirements of reducing the circulating current, ensuring that the voltage increase amplitude is not large and being convenient for replacing the damaged circulating current restrainer, so that the operation reliability of the power grid is improved.
Disclosure of Invention
Aiming at the problems that the existing circulating current restraining methods such as series resistance, inductance and impedance are expensive to implement, the voltage of a sheath rises, a circulating current suppressor is not easy to replace and the like, the high-voltage cable metal sheath grounding circulating current restraining method based on the electromagnetic coupling method is provided on the basis of ensuring that the circulating current of a cable is reduced and the normal operation of the cable is not influenced, the normal operation of the cable is ensured, and the continuity and reliability of power supply and distribution of a power system are further improved.
In order to achieve the purpose, the invention adopts the following technical scheme: the method for restraining the grounding circulation of the metal sheath of the high-voltage cable based on the electromagnetic coupling method is characterized by comprising the following steps of:
the method for restraining the grounding circulation of the metal sheath of the high-voltage cable based on the electromagnetic coupling method comprises the steps that the metal sheath of a running high-voltage cable line is divided into a plurality of large sections, then each large section is divided into three small sections on average, the metal sheaths are connected in a cross transposition mode through cross interconnection boxes between the sections of the small sections, then the metal sheaths at the head end and the tail end are connected and converged and then grounded, and a circulation suppressor based on the electromagnetic coupling method is connected to the terminal of the metal sheaths;
the circular current suppressor based on the electromagnetic coupling method is that a grounding wire at the terminal of each phase of metal sheath is used as a primary coil and then grounded, and a pair of resistance-inductance pairs is connected in series at the secondary side to be used as a suppressor.
The series connection suppressor impedance is approximately 3-4 times of the equivalent impedance value of the metal sheath, and the impedance values of the resistor and the inductor are kept consistent.
The primary side coil and the secondary side coil of the suppressor are optimally selected to be consistent in number, and the requirements of small enough no-load current and small temperature rise can be met when the number of the coils is about 100.
Wherein, the magnetic core is formed by winding silicon steel sheets, and sufficient magnetic flux is ensured.
Compared with the mode of directly connecting resistors, inductors and resistor-inductor suppressors in series in the prior art, the method for suppressing the grounding circulation of the high-voltage cable metal sheath based on electromagnetic coupling cancels the contact on the cable metal sheath, avoids the influence on the normal operation of the cable when the suppressors are in failure, and simultaneously ensures the good suppression effect of the grounding circulation of the cable.
Secondly, the calculation shows that when the series resistance value is close to 3-4 times of the equivalent resistance value of the sheath, the suppression effect is best when the number of turns of the primary side coil is the same as that of the secondary side coil.
In conclusion, the method for restraining the grounding circulation of the metal sheath of the high-voltage cable by electromagnetic coupling can obtain a better circulation restraining effect.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:
FIG. 1 is a schematic diagram of a cross-connect grounding cable employing an electromagnetic coupling based suppression method;
FIG. 2 is a schematic diagram of an electromagnetic coupling based suppressor;
FIG. 3 shows the results of the grounding loop current test of the metal sheath connected in series at different impedance values;
FIG. 4 is a graph of the results of a ground loop test using metal jackets of different coil ratios;
the specific implementation mode is as follows:
a high-voltage cable metal sheath grounding circulation suppression method based on an electromagnetic coupling method is shown in fig. 1, wherein an electromagnetic coupling circulation suppressor is installed at the terminal end (shown as a figure number 1) of each metal sheath; as shown in fig. 2, the electromagnetic coupling suppressor includes an impedance suppressor sealed and connected in series by potting an epoxy potting body 2 in an insulating housing material 1, and the impedance suppressor is connected to a coil on the secondary side of a magnetic core 5 by a lead 4 extending from the insulating housing material 3, and the coil on the primary side of the magnetic core 5 is connected to a cable sheath and then grounded. The insulating shell material 1 is preferably a silicone rubber sleeve, and the magnetic core 5 is formed by winding a silicon steel sheet.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
The invention relates to a high-voltage cable metal sheath grounding circulation restraining method based on an electromagnetic coupling method, which adopts a high-voltage cable metal sheath electromagnetic coupling circulation restraining system, and comprises the steps of dividing a metal sheath of a running high-voltage cable line into a plurality of large sections, then averagely dividing each large section into three small sections, carrying out cross transposition connection on the metal sheath through cross interconnection boxes between the sections of the small sections, then connecting and converging the metal sheaths at the head end and the tail end, then grounding, and connecting a circulation restraining device based on the electromagnetic coupling method at the terminal of the metal sheath;
the circular current suppressor based on the electromagnetic coupling method is that a grounding wire at the terminal of each phase of metal sheath is used as a primary coil and then grounded, and a pair of resistance-inductance pairs is connected in series at the secondary side to be used as a suppressor.
The series connection suppressor impedance is approximately 3-4 times of the equivalent impedance value of the metal sheath, and the impedance values of the resistor and the inductor are kept consistent.
The primary side coil and the secondary side coil of the suppressor are optimally selected to be consistent in number, and the requirements of small enough no-load current and small temperature rise can be met when the number of the coils is about 100.
Wherein, the magnetic core is formed by winding silicon steel sheets, and sufficient magnetic flux is ensured.
Specifically, as shown in fig. 1, an electromagnetically coupled circulation suppressor is installed at a terminal end (as shown by reference numeral 1) of each metal sheath; as shown in fig. 2, the electromagnetic coupling suppressor includes an impedance suppressor sealed and connected in series by potting an epoxy potting body 2 in an insulating housing material 1, and the impedance suppressor is connected to a coil on the secondary side of a magnetic core 5 by a lead 4 extending from the insulating housing material 3, and the coil on the primary side of the magnetic core 5 is connected to a cable sheath and then grounded. The insulating shell material 1 is preferably a silicone rubber sleeve, and the magnetic core 5 is formed by winding a silicon steel sheet.
The electromagnetic coupling based loop current suppression method is verified by selecting the impedance, core loop current and coil ratio of different suppressors according to the cable data shown in table 1. When the currents of the cable cores are different, the result of the grounding circulation is shown in fig. 3, and the grounding circulation can be well inhibited, and the inhibiting effect is better when the impedance is 3-4 times of the equivalent impedance of the sheath. The effect of suppressing the ground circulating current when the number of turns of the primary side coil and the number of turns of the secondary side coil of the magnetic core are different is shown in fig. 4, and it can be seen from the figure that the effect of suppressing the ground circulating current is good when the number of turns of the coil is different, and the electromagnetic loss is small when the number of turns of the coil is the same. Verification shows that the electromagnetic coupling-based high-voltage cable grounding circulation restraining method has a good restraining effect on grounding circulation, and when the impedance of the suppressor is 3-4 times of the equivalent impedance of the sheath, the circulation restraining effect is the best when the primary side coil and the secondary side coil are the same.
TABLE 1 Cable data
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (3)
1. The method for restraining the grounding circulation of the metal sheath of the high-voltage cable based on the electromagnetic coupling method is characterized by comprising the following steps:
the high-voltage cable metal sheath grounding circulating current suppression system based on the electromagnetic coupling method is adopted, the high-voltage cable metal sheath grounding circulating current suppression method based on the electromagnetic coupling method comprises the steps that a three-phase high-voltage cable line is divided into a plurality of large sections, then each large section is divided into three average small sections, each small section is subjected to cross transposition through a cross interconnection box, a metal sheath grounding protector is installed in the cross interconnection box, a head end metal sheath and a tail end metal sheath are connected and then grounded, and a circulating current suppressor of the electromagnetic coupling method is connected to a metal sheath terminal.
The circular current suppressor based on the electromagnetic coupling method is that a jacket grounding wire at the tail end of each metal jacket penetrates through a magnetic core to serve as a primary coil and then is grounded, and a pair of resistance-inductance pairs are connected in series on the secondary side to serve as a suppressor.
2. The method for suppressing the grounding circulating current of the metal sheath of the high-voltage cable based on the electromagnetic coupling method as recited in claim 1, wherein:
according to the circulating current restraining method, when the coils of the primary side and the secondary side are consistent, the circulating current restraining effect is optimal when the impedance value of the resistance-inductance pair is 3-4 times of the impedance value of the cable sheath, and the circulating current restraining effect can be optimal when the series impedor is gradually reduced along with the increase of the coils of the secondary side.
3. The method for suppressing the grounding circulating current of the metal sheath of the high-voltage cable based on the electromagnetic coupling method as recited in claim 1, wherein:
the electromagnetic coupling method suppressor comprises an impedance suppressor which is sealed and connected in series by pouring epoxy casting in an insulating shell material, and the impedance suppressor is connected with a coil on the secondary side of a magnetic core through a lead extending from the insulating shell material, and a coil on the primary side of the magnetic core is connected with a cable sheath and then grounded. The insulating shell is preferably made of a silicon rubber sleeve, and the magnetic core is formed by winding a silicon steel sheet.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010771515.7A CN111884175A (en) | 2020-08-06 | 2020-08-06 | High-voltage cable metal sheath grounding circulation restraining method based on electromagnetic coupling method |
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| CN202010771515.7A CN111884175A (en) | 2020-08-06 | 2020-08-06 | High-voltage cable metal sheath grounding circulation restraining method based on electromagnetic coupling method |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114034905A (en) * | 2021-11-08 | 2022-02-11 | 浙江华云电力工程设计咨询有限公司 | Cable metal sheath grounding circulation calculation method based on multi-conductor transmission line theory |
Citations (3)
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|---|---|---|---|---|
| US20020171991A1 (en) * | 2001-05-15 | 2002-11-21 | Fowler William J. | Lightning suppression system for control or instrumentation cable |
| CN207782491U (en) * | 2018-01-30 | 2018-08-28 | 武汉大学 | A kind of cable bushing circular current sensing electricity getting device |
| CN110380377A (en) * | 2019-07-23 | 2019-10-25 | 刘勇 | A kind of synthesis circulation inhibition method of high-voltage cable metal sheath |
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2020
- 2020-08-06 CN CN202010771515.7A patent/CN111884175A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20020171991A1 (en) * | 2001-05-15 | 2002-11-21 | Fowler William J. | Lightning suppression system for control or instrumentation cable |
| CN207782491U (en) * | 2018-01-30 | 2018-08-28 | 武汉大学 | A kind of cable bushing circular current sensing electricity getting device |
| CN110380377A (en) * | 2019-07-23 | 2019-10-25 | 刘勇 | A kind of synthesis circulation inhibition method of high-voltage cable metal sheath |
Non-Patent Citations (2)
| Title |
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| 刘文胜 等: "《电路分析简明教程》", 31 August 2018, 华中科技大学出版社 * |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114034905A (en) * | 2021-11-08 | 2022-02-11 | 浙江华云电力工程设计咨询有限公司 | Cable metal sheath grounding circulation calculation method based on multi-conductor transmission line theory |
| CN114034905B (en) * | 2021-11-08 | 2024-04-02 | 浙江华云电力工程设计咨询有限公司 | Cable metal sheath grounding circulation calculation method based on multi-conductor transmission line theory |
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